Props or jacks



July 1, 1962 R. REYNOLDS ET AL PROPS OR JACKS Filed March 10, 1961 United States Patent 3,046,949 PROPS 0R SACKS Reginald Reynolds and Peter Haig Stammers, Saffron Walden, England, assignors to Acrow (Engineers) Limited, London, England Filed Mar. 10, 1961, Ser. No. 94,758 Claims priority, application Great Britain Mar. 14, 1960 3 Claims. (Cl. 12146) This invention relates to hydraulic props of the type comprising a ram working in a cylinder the ram being extendable from the cylinder on introduction of hydraulic fluid to a pressure chamber in the cylinder below the (Such props will hereafter be referred to as props of the type described) As such props have sometimes to be man-handled below ground in encumbered surroundings, it is advantageous that they be of reasonably light weight. It is however, difiicult to fulfill that requirement whilst maintaining sufficient strength for other requirements.

One part which offers an opportunity of efiecting a substantial saving in weight is the head of the ram of the prop but in so doing care has to be taken to ensure that there is a sufiiciently great area of contact with the cylinder of the ram to provide against leakage and also to provide lateral stability when the ram is at the top or its stroke and is engaging to a minimum extent in the cylinder.

The expedient which is adopted in accordance with this invention is to provide, for connection of the head to the barrel of the ram, two half shells which are held in position radially by the ram cylinder and which hold the head and the barrel against relative axial movement. This leads to simplicity of construction, assembly and disassembly and allows the thickness of the head to be reduced to that which is made necessary by the provision of valves, the bearing area being provided not by the head of the ram but by the shells.

The shells are preferably provided with two inwardly projecting rims or shoulders one to engage in a groove in the barrel and the other in a groove or beneath a shoulder, in the ram head.

An example of a construction of a prop in accordance with the invention is shown in the accompanying drawing in which:

FIGURE 1 is an elevation of a prop with the lower end in cross section; and

FIGURE 2 is a plan view of the two shells.

The hydraulic prop comprises essentially a ram 2 with a head part 3 to engage the load, working within a cylinder 4. The ram is moved out from the top of the cylinder when hydraulic fluid, carried in a reservoir formed by the barrel 6 of the ram, is pumped, by reciprocation by means (not shown) of a low pressure piston 7 and a high pressure piston 9, from the reservoir to a pressure chamber 8 in the cylinder past a main valve 10 in the head 12 of the ram.

The ram head 12 which carries the main valve 16 and a yield valve 14, is attached to the barrel 6 of the ram by means of two semi-cylindrical shells 16 made of a suitable bearing metal such as Main metal. The shells have an inwardly projecting rim 18 at their upper edge which engages in a groove 20 in the barrel. The lower end of the shells is formed with a shoulder 22 which engages under a corresponding shoulder 24 on the ram head. The shells are assembled around the barrel and head with the rims 18 engaging in the groove 26 and the Ice shoulder 22 and 24 abutting and the assembly is then inserted into the cylinder 4. In this position the shells are held radially by their engagement with the cylinder walls and they thus hold the head and the barrel of the ram axially together.

The shells to have a portion 26 of increased thickness at their upper and lower ends which projects slightly outwardly from the remaining portion of the shell, and it is these thick portions which engage the inner walls of the cylinder 4 and provide the bearing area for movement of the ram within the cylinder. Due to the length of the portion of the shells between the bearing portions 26 which is not in contact with the side of the cylinder, suriace'friction is minimized whilst at the same time due to the distance between the bearing portions 26 the bearing area is well distributed to preventundue lateral rocking of the ram within the cylinder.

When the ram is fully extended it is prevented from wholly moving out from the cylinder by the abutment of the top of the shells against a collar 23 provided near the upper end of the cylinder. It will be appreciated that when the shells abut the collar the whole depth of the shells will still be within the cylinder. Thus the bearing portions at the top and bottom of the shells will still provide a good deal of lateral stability.

It is beneficial to provide a slight clearance between the shells and the ram head 12 so that the shells can move slightly relative to the ram head enabling them to be selfcentering in the cylinder and to be a better fit in the cylinder than would otherwise be possible. As the lower end face of the shells rests on an oil seal 34 surrounding the ram head, the seal is prevented irom extruding up between the ram and the cylinder even when the prop is subjected to considerable loads and is set at an angle.

It will be appreciated that the ram head need only be thick enough to accommodate the valves 10 and 14, the required bearing surfaces being provided by the shells so that a saying in weight is achieved as compared with props in which the ram head has to be sufficiently thick, with consequent increased weight, to provide an adequate bearing area.

We claim:

1. A hydraulic prop comprising a cylinder, a ram working in the cylinder said ram having a barrel and a head, and two half shells of bearing metal connecting the said barrel and head of the ram, said half shells being held in position radially by contact with the ram cylinder and each being provided with an inwardly projecting rim at each end engaging a corresponding abutment surface on the ram head and barrel to hold said ram head and barrel against relative axial movement.

2.. A hydraulic prop as claimed in claim 1 in which the abutment surface on .the ram barrel is provided with a groove and the abutment surface on the ram head is provided by a shoulder.

3. A hydraulic prop as claimed in claim 1 in which the upper and lower portions of each of the shells extends out from the intermediate portion of the shells to form hearing surfaces which contact the inner wall of the cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,661,721 Sherwen Dec. 8, 1953 2,821,264 Ulinski Jan. 28, 1958 2,928,379 Perciado Mar. 15, 1960 

